JP2817181B2 - Manufacturing method of Bi-based superconducting ceramics sheet with high critical current density - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention hot-presses an amorphous thin plate of Bi-Sr-Ca-Cu-O-based superconducting composite oxide (hereinafter referred to as Bi-based superconducting composite oxide). The present invention relates to a method for growing a crystal in a certain direction and producing a Bi-based superconducting ceramic thin plate having an excellent critical current density. Here, the Bi-based superconducting ceramic sheet is not limited to the Bi-based superconducting ceramic sheet, but is
It includes a laminate of a superconducting ceramic thin plate.

[Prior Art] Conventionally, a Bi-based superconducting ceramic thin plate has been manufactured as follows.

First, as raw material powders, Bi oxide (hereinafter referred to as Bi ₂ O ₃ ), Sr carbonate (hereinafter referred to as SrCO ₃ ), Ca carbonate (hereinafter referred to as CaCO ₃ ), and Cu oxide (Hereinafter, referred to as CuO) powder, these raw material powders are blended in a predetermined ratio, and after mixing, the mixed powder is heated at a temperature of 750 to 90.
It is kept at 0 ° C. for a predetermined time and fired to produce a Bi-based superconductive composite oxide. The Bi-based composite oxide thus obtained is pulverized and then fired again. The firing and pulverization are repeated two or three times, and finally pulverized to obtain a Bi-based superconducting composite oxide powder. The Bi-based superconducting composite oxide powder prepared above is mixed with an organic vehicle or an organic binder, formed into a coating or a thin plate by a coating method or a doctor blade method, respectively, and after drying the formed body, in air, temperature: 200 to 400 ° C., degreased under the conditions of 50 to 80 hours, and cooled in a furnace to produce a film or a thin plate-shaped degreased body.The degreased body is further heated in air at a temperature of 700 to 900 ° C., 20 to 40. Heat treatment under the condition of holding time, B
An i-based superconducting ceramic coating or thin plate was produced.

[Problems to be solved by the invention]

However, the Bi-based superconducting composite oxide powder is not only inconsistent in the crystal orientation of the powder itself, but also by mixing the powder with an organic vehicle or organic binder, and coating or thin plate formed by coating or doctor blade method. The crystal orientation of the Bi-based superconducting composite oxide powder contained therein is also random, which causes a problem that the critical current density of the coating or thin plate is not improved.

[Means for solving the problem]

Therefore, the present inventors conducted research to produce a Bi-based superconducting ceramic thin plate having an excellent critical current density. Hot pressing in the direction
The crystal grows perpendicular to the pressing direction to become a Bi-based superconducting ceramic thin plate, and it has been found that the Bi-based superconducting ceramic thin plate having this orientation has an excellent critical current density.

The present invention has been made based on such knowledge, and has produced an amorphous thin plate of a Bi-based superconducting composite oxide,
The present invention is characterized by a method of manufacturing a Bi-based superconducting ceramic thin plate having a high critical current density by hot pressing while applying pressure to both surfaces of the thin plate.

The hot pressing pressure applied to both sides of the thin plate is 100 ~ 8
00 kg / cm ² , and the hot press temperature is preferably in the range of 600 to 880 ° C.

If the above hot press temperature is lower than 600 ° C, amorphous crystallization occurs but no superconducting phase is generated.On the other hand, if the temperature exceeds 880 ° C, the crystals are partially melted and crystals having orientation cannot be obtained. The temperature was set at 600-880 ° C.

Furthermore, if the hot pressing pressure is less than 100 kg / cm ² , the crystals will not be oriented.On the other hand, even if hot pressing is performed at a pressure exceeding 860 kg / cm ² , the plastic flow will be severe and the orientation will be weakened. Is defined as 100 to 800 kg / cm ² .

When heating the Bi-based superconducting composite oxide amorphous thin plate while pressing both sides so as to satisfy the conditions of the present invention,
Since the crystal grows perpendicular to the pressing direction, the a-b plane of the crystal is oriented parallel to the thin plate, and the current generally flows parallel to the a-b plane, the critical current density J _{C of the} hot-pressed thin plate becomes large. Is considered to be greatly improved. The atmosphere of the hot press may be performed in any of vacuum, inert gas, and air.

〔Example〕

Next, the present invention will be specifically described based on embodiments.

Example 1 Bi ₂ O ₃ powder, SrCO ₃ powder, CaCO ₃ powder and CuO powder were prepared as raw material powders, and these powders were prepared as Bi ₂ O ₃ powder: 7.284 g, SrCO ₃ powder: 4.614 g, CaCO ₃ powder : 3.128 g, CuO powder: 4.974 g, were weighed and mixed in a ball mill for 2 hours. This mixed powder was heated and melted at a temperature of 1150 ° C., and then the melt was ultra-quenched by a normal twin-roll method to obtain a B: 40 μm thick
An amorphous tape of i-based superconducting composite oxide was prepared.

This amorphous tape was cut into a size of width: 10 mm × length: 20 mm to prepare a test piece tape. These test piece tapes were hot-pressed in a vacuum atmosphere of 1 × 10 ⁻³ Torr under the conditions shown in Table 1. The hot pressing pressure was applied so as to clamp the test piece tape on both sides.

Hot pressed body test piece manufactured in this way The superconducting critical temperature and absolute temperature of the tape were measured by a four-terminal method at a temperature of 77.3 ° K, and the superconducting critical temperature and critical current density shown in Table 1 were obtained.

The SEM observation of the fracture surface of the hot-pressed specimen tape obtained by hot-pressing under the conditions of the method 9 of the present invention shown in Table 1 was carried out, and as a result, the crystal structure oriented perpendicular to the pressing direction as shown in FIG. Was seen.

For comparison, the test piece tape was hot-pressed at a temperature and pressure outside the conditions of the production method of the present invention, and the superconducting critical temperature and the absolute temperature of the hot-pressed body obtained at that time were 77.
The critical current density at 3 ゜ K was measured, and the critical temperature and absolute temperature of the superconducting king of Bi-based superconducting ceramic thin plates manufactured by the conventional doctor blade method at 77.3 ゜ K were also measured. The results are shown in Table 1.

Example 2 Each of Ag thin plate, Hastelloy thin plate having dimensions of width: 10 mm × length: 20 mm × thickness: 1 mm, A stainless steel thin plate, a MgO single crystal thin plate, and a SrTiO ₃ single crystal thin plate were prepared, and these thin plates were made of the Bi-based superconducting composite oxide amorphous thin plate prepared in Example 1, and had a width of 10 m.
m × length: 20mm × thickness: 4μm with a test piece tape,
Lamination was performed as shown in Table 2 to produce a laminate.

These laminates were vacuum hot-pressed at 10 ⁻³ Torr under the conditions shown in Table 2 to produce a laminated thin-plate hot-pressed body.
The superconducting critical temperature and the critical current density at an absolute temperature of 77.3 ° K of the hot-pressed laminated sheet were measured by a four-terminal method, and the results are also shown in Table 2.

From the results shown in Table 2, it can be seen that even a Bi-based superconducting ceramic laminated sheet obtained by laminating an Bi-based superconducting composite oxide amorphous sheet on a metal sheet has an excellent critical current density.

〔The invention's effect〕

Each of the Bi-based superconducting ceramic sheets obtained by the production method of the present invention has an excellent superconducting critical temperature and critical current density, and the laminated sheet of the Bi-based superconducting ceramic sheet and the metal sheet is a metal sheet on the substrate. Therefore, it is possible to provide an excellent Bi-based superconducting ceramic sheet which has excellent superconducting critical temperature and high critical current density, and also has excellent strength and at the same time, can be used industrially. it can.

[Brief description of the drawings]

FIG. 1 is an SEM observation diagram of a Bi-based superconducting ceramic thin plate obtained by hot pressing.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-239054 (JP, A) JP-A-2-51467 (JP, A) JP-A-2-64019 (JP, A) JP-A-2- 133320 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 1/00-57/00 H01L 39/00-39/24 H01B 12/00-13/00

Claims (4)

(57) [Claims] An amorphous thin plate of Bi-Sr-Ca-Cu-O-based superconducting composite oxide (hereinafter referred to as Bi-based superconducting composite oxide) is hot-pressed in a direction perpendicular to the surface thereof. Of Bi-based superconducting ceramics sheet with high critical current density. 2. The hot press is performed at a temperature of 600 to 880 ° C.
Pressure: 100~800kg / cm preparation of Bi-based superconducting ceramic thin plate having a high critical current density according to claim 1, wherein the ² by performing. 3. A Bi-based superconducting ceramic thin plate having a high critical current density according to claim 1, wherein a laminate of the Bi-based superconducting composite oxide amorphous thin plate and the metal thin plate is hot-pressed. Manufacturing method. 4. A laminate obtained by laminating an amorphous thin plate of the Bi-based superconducting composite oxide on a metal thin plate via a buffer thin plate made of a metal oxide, and hot pressing the laminate. With high critical current density
A method for manufacturing Bi-based superconducting ceramic thin plates.